Method of abrading a zirconium-based alloy workpiece

ABSTRACT

A method of abrading a zirconium-based alloy workpiece including the steps of contacting a zirconium-based alloy workpiece with an abrasive article, wherein the abrasive article includes a flexible waterproof backing having a first surface bearing a cured primer coating; and a plurality of shaped structures, each structure having a distal end spaced from said backing and an attachment end attached to the primer coating on the backing, said shaped structures comprising a mixture of abrasive particles having a Knoop hardness greater than 2,200 kg/mm 2  and cured particulate binder, wherein the metal workpiece is contacted with the distal ends of the shaped structures to form an abrading interface; moving the abrasive article relative to the metal workpiece while providing sufficient force between the metal workpiece and the distal ends of the shaped structures of the abrasive article to abrade the metal workpiece; and applying liquid coolant proximate the abrading interface.

CROSS-REFERENCE

This application claims priority to previously filed U.S. ProvisionalApplication No. 60/882,938, entitled “METHOD OF ABRADING AZIRCONIUM-BASED ALLOY WORKPIECE” filed on Dec. 31, 2006.

FIELD

The present disclosure relates generally to a method of abrading asurface of a zirconium-based alloy workpiece.

BACKGROUND

Materials comprising zirconium based alloys have found utility in thenuclear power industry. One specific application in this industry is theuse of zirconium-based alloy tubes as cladding for fuel pellets. Theenvironment to which the tubes are exposed during this application cancause corrosion of the tube's exposed surface that often limits theduration of their use. Improving corrosion resistance is desirable andhas been related to the tube's surface finish immediately prior to use.Improved corrosion resistance has been observed with a decreasing levelof surface roughness, i.e., creating a smoother initial surface finishof the tube.

Several surface finishing processes have been employed to improve thesurface finish of the tubes prior to use including a pickling method anda mechanical abrading method. The pickling method relies on strong acidsto modify the surface finish of the zirconium based alloy. Themechanical abrading method allows at least portions of the surface ofzirconium-based alloy workpiece to be modified by the urging of anabrasive article against the workpiece. The mechanical abrading methodoften employs a complicated, multi-step abrading process requiring aseries of abrasive articles, of varying abrasive particle grit size, runin specific sequences for various times, pressures, and/or cycles.

The mechanical abrading method is often considered a better alternativethat the chemical method. However, there is a continuing need for amechanical abrading method that can simplify the surface finishingprocess, provide improved surface finish, provide improved processthroughput, i.e., improved removal rate of the zirconium-based alloy,and/or lower the cost of the surface finishing process.

SUMMARY

The present disclosure relates generally to a method of abrading asurface of a zirconium-based alloy cylindrical workpiece. Morespecifically, the methods of the present disclosure have been shown toprovide significant and unexpected performance advantages overconventional coated abrasives when used to abrade zirconium-based alloycylindrical workpieces in the presence of a liquid coolant. Usingmethods of the present disclosure, an abrasive article can be used toachieve a desired finish with a higher cut rate than conventional coatedabrasives. In some applications, the methods of the present disclosurereduce the necessity of using multiple abrasive article grades toachieve a target surface finish.

In one aspect, the present disclosure relates to a method of abrading azirconium-based alloy workpiece that includes providing an abrasivearticle having a flexible waterproof backing having a first surfacebearing a cured primer coating; and a plurality of shaped structures,each structure having a distal end spaced from said backing and anattachment end attached to the primer coating on the waterproof backing,said shaped structures comprising a mixture of abrasive particles havinga Knoop hardness greater than 2,200 kg/mm² and cured particulate binder.The method includes contacting the zirconium-based alloy workpiece withthe distal ends of the shaped structures to form an abrading interface,and moving the abrasive article relative to the zirconium-based alloyworkpiece while providing sufficient force between the zirconium-basedalloy workpiece and the distal ends of the shaped structures of theabrasive article to abrade the zirconium-based alloy workpiece. Themethod also includes applying liquid coolant proximate the abradinginterface.

In some embodiments, the abrasive article is an abrasive belt.

In some embodiments, the abrasive particles comprise silicon carbide.

In some embodiments, the flexible waterproof backing is a treated wovenpolyester fabric.

In some embodiments, the liquid coolant is a mixture comprising an oil.

In some embodiments, the workpiece is rotated while the workpiece isabraded. An abrasive article can be mounted on a centerless grindingmachine. In some embodiments, an abrasive belt can be mounted on a fixedcenter roll grinding machine.

In some embodiments, at least a portion of the shaped structures of theabrasive article comprise a cross-section selected from the groupconsisting of square, circular, rectangular, hexagonal, and triangular.The shaped structures can be arranged in a tessellated pattern. In someembodiments, the shaped structures can be formed by an embossingprocess.

In another aspect, the present disclosure relates to a method ofabrading a zirconium cylindrical workpiece by providing an abrasivearticle having a flexible waterproof backing having a first surfacebearing a cured primer coating; and a plurality of shaped structures,each structure having a distal end spaced from said backing and anattachment end attached to the primer coating on the waterproof backing,said shaped structures comprising a mixture of silicon carbide abrasiveparticles, and a cured thermoset particulate binder. The method includescontacting the zirconium cylindrical workpiece with the distal ends ofthe shaped structures to form an abrading interface and moving theabrasive article relative to the zirconium cylindrical workpiece whileproviding sufficient force between the zirconium cylindrical workpieceand the distal ends of the shaped structures of the abrasive article toabrade the zirconium cylindrical workpiece while applying liquid coolantproximate the abrading interface.

In some embodiments, silicon carbide abrasive particles having anaverage particle size in the range of 4 to 40 micrometers are used.

The methods of the present disclosure can be used to obtain at least 0.3grams of material removal from the workpiece per 25.4 millimeter of beltwidth per minute, and a surface finish no greater than 0.22 micrometersRa, or no greater than 0.20 micrometers Ra, or even no greater than 0.13micrometers Ra.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1A is a top view of a section of an abrasive article used inaccordance with methods of the present disclosure;

FIG. 1B is a side view of the section of the abrasive article shown inFIG. 1A;

FIG. 2A is a top view of a section of another abrasive article used inaccordance with methods of the present disclosure; and

FIG. 2B is an enlarged schematic cross-section of a portion of theabrasive article depicted in FIG. 2A, taken at line 2B-2B.

These figures, which are idealized, are intended to be merelyillustrative of the abrasive article of the present disclosure andnon-limiting.

DETAILED DESCRIPTION

The present disclosure refers to abrasive articles. The abrasivearticles used in methods as disclosed herein have an endless abrasivesurface (hereinafter “endless abrasive article”). Examples of endlessabrasive articles include, but are not limited to, endless abrasivebelts and endless abrasive bands. Endless abrasive articles also includeassembled articles comprising abrasive sheets or strips endlesslydisposed and removably or permanently affixed to the circumference of arotatable cylinder so as to present an endless abrasive surface to aworkpiece, when rotated. Examples of such assembled articles include,but are not limited to, sanding drums, wheels, and helically-wrappedcylinders. In an embodiment, the rotatable cylinder can have surfacecharacteristics or surface constructions that can be chosen based atleast in part on the desired use of the article. Examples of varioussurfaces include, but are not limited to, hard surfaces such as steel orhigh-durometer elastomeric surfaces, and soft surfaces such as foam orlow-durometer elastomeric surfaces; or air-filled wheels.

The term “backing” refers to a flexible sheet material which willwithstand use conditions of an abrasive product of the type hereindescribed;

The term “shaped structures” refers to a structure having threedimensions including height, width and depth, such as, for example, acube, rectangular block, right cylinder, rib, hexagonal based pyramid,truncated cone or truncated pyramid;

The term “temporary shaped structure” refers to a shaped structurecomprising components in a transitory state that may be easily deformedby slight contact until it is converted to a permanent shaped structure;

The term “particulate curable binder” refers to binder materials thatare solid at room temperature, have been processed to provide particles,and that may be softened and cured either upon heating and subsequentcooling, if thermoplastic, or upon sufficient exposure to heat or othersuitable energy source, if thermosetting or cross-linkable;

The term “cured particulate binder” refers to a binder that was formerlyparticulate that has been softened and cured to form a cured mass ofbinder that no longer has particulate characteristics;

The term “permanent shaped structure” refers to a shaped structure thatwill not be altered by slight contact except when it is employed toabrade or otherwise modify the surface of a workpiece;

The term “softening” with reference to the particulate binder materialrefers to converting the particulate binder material from a solid havinga defined particle shape to a physical form that no longer has thedefined shape but instead is flowable as a liquid, viscous liquid, orsemi-liquid mass;

The term “cured” with reference to the curable binder or primer materialmeans that the material has been hardened to such a degree that theresulting product will function as an abrasive product;

The term “perforated-sheet patterning process” when referring to aprocess of forming the temporary shaped structures refers to any processthat urges the particulate curable binder-abrasive particle mixturethrough a perforated sheet or cylinder and onto a backing, the holes insaid sheet that form the perforations being shaped and configured toproduce the desired shape and pattern of the temporary shapedstructures.

The above summary of the abrasive article of the present disclosure isnot intended to describe each disclosed embodiment of everyimplementation of the abrasive article of the present disclosure. Thefigures and the detailed description that follow more particularlyexemplify illustrative embodiments. The recitation of numerical rangesby endpoints includes all numbers subsumed with that range (e.g., 1 to 5includes 1, 1.5, 2, 2.75, 3, 4, 4.80, and 5).

FIG. 1A, not drawn to scale, is a top view of an abrasive article usefulin the methods of the present disclosure. It will be noted that cutlines 14 and 12 intersect to provide shaped abrasive structures 10having distal ends 16 and sidewalls 18 on backing 19 as depicted inFIGS. 1A and 1B.

FIGS. 2A and 2B, not drawn to scale, show an abrasive product 20 thatincludes backing 21, primer coating 22 and a plurality of shapedstructures 23. Each shaped body includes abrasive particles 24 that arebonded together by cured particulate binder material 25. The shapedbodies in FIGS. 2A and 2B are truncated cones having flattened tops 26.

Descriptions of apparatuses and methods useful for making the abrasivearticles used in accordance with methods of the present disclosure arefound in, for example, U.S. Pat. No. 6,833,014 (Welygan et al) and U.S.Pat. No. 7,044,989 (Welygan et al) and U.S. Pat. Pub. No. 2007/0074455(Welygan et al), the disclosures of which are incorporated herein byreference. Abrasive articles employed in the method of the presentdisclosure comprise a flexible waterproof backing having a first surfacebearing a cured primer coating and a plurality of shaped structures eachstructure having a distal end spaced from said backing and an attachmentend attached to the primer coating on the waterproof backing, saidshaped structures being comprised of a mixture of abrasive particles andcured particulate. Descriptions of the abrasive articles includingabrasive belts can be found in, for example, U.S. Pat. No. 6,833,014(Welygan et al) and U.S. Pat. No. 7,044,989 (Welygan et al) and U.S.Pat. Pub. No. 2007/0074455 (Welygan et al).

As used herein, the term “waterproof backing” refers to a backing withsufficient wet strength to resist tearing or other damage in wetabrading operations. Useful flexible waterproof backings include, forexample, flexible polymeric film and primed polymeric film, metal foil,woven fabrics, knit fabrics, stitchbonded fabrics, coated paper,flexible vulcanized fibre, nonwoven fabric, calendared nonwoven fabric,open cell foam, closed cell foam, treated versions of the foregoing, andcombinations thereof. The waterproof backing may be porous or nonporous.

As mentioned above, the waterproof backing may have one or moretreatments thereon, which treatment(s) may cover at least a portion of afirst major surface. Examples of such treatments include uncured,partially cured, or cured primers, tie layers, saturants (i.e., abarrier coat that is coated on all exposed surfaces of the waterproofbacking), presizes (i.e., a barrier coat overlying the major surface ofthe waterproof backing onto which the abrasive layer is applied), andbacksizes (i.e., a barrier coat overlying the major surface of thewaterproof backing opposite the major surface on which the abrasivelayer is applied). Useful presize, backsize and saturant compositionsinclude glue, phenolic resins, latices, epoxy resins, urea-formaldehyde,urethane, melamine-formaldehyde, neoprene rubber, butyl acrylate,styrol, starch, and combinations thereof.

In some embodiments, the waterproof backing comprises a scrim. In suchembodiments, it is typically desirable to support the scrim on a carrierto prevent the particulate curable binder precursor from passing throughthe scrim and creating processing problems.

The scrim may comprise an open mesh selected from the group consistingof woven, nonwoven, or knitted fiber mesh; synthetic fiber mesh; naturalfiber mesh; metal fiber mesh; molded thermoplastic polymer mesh; moldedthermoset polymer mesh; perforated sheet materials; slit and stretchedsheet materials; and combinations thereof.

In some embodiments, the scrim may be made of natural or syntheticfibers, which may be either knitted or woven in a network havingintermittent openings spaced along the surface of the scrim. The scrimneed not be woven in a uniform pattern but may also include a nonwovenrandom pattern. Thus, the openings may either be in a pattern orrandomly spaced. The scrim network openings may be rectangular or theymay have other shapes including a diamond shape, a triangular shape, anoctagonal shape or a combination of shapes.

Any of a variety of materials are suitable for use as the carrier,including for example heat resistant polymeric films, metal foils, wovenfabrics, paper, calendared nonwoven fabrics, treated versions thereof,and combinations thereof. The thickness of a carrier is generally notimportant as long as it has sufficient integrity to be separated fromthe scrim.

Details concerning curable primers that can be useful for adhering theshaped structures to the waterproof backing may be found in, forexample, U.S. Pat. No. 7,044,989 (Welygan et al). The primer coating maycomprise a mixture of at least two different binder materials. In someembodiments, the primer material is a thermosetting binder. In someembodiments, primers are particulate mixtures of first particles of athermosettable resin (e.g., a thermosettable polyester resin) and secondparticles of thermoplastic resin particles (e.g., thermoplasticpolyester particles).

Abrasive articles useful in the methods of the present disclosurecomprise at least one shaped structure that includes a plurality ofabrasive particles dispersed in a cured particulate binder. The abrasiveparticles may be uniformly dispersed in a binder or alternatively theabrasive particles may be non-uniformly dispersed therein. In someembodiments, the abrasive particles are uniformly dispersed in thebinder so that the resulting abrasive product has a more consistentcutting ability.

Exemplary abrasive particles include but are not limited to fusedaluminum oxide, heat treated aluminum oxide, white fused aluminum oxide,black silicon carbide, green silicon carbide, titanium diboride, boroncarbide, titanium carbide, diamond (both natural and synthetic), cubicboron nitride, and sol gel abrasive particles of appropriate hardness,and combinations thereof. Examples of sol gel abrasive particles can befound in U.S. Pat. No. 4,314,827 (Leitheiser et al.); U.S. Pat. No.4,623,364 (Cottringer et al); U.S. Pat. No. 4,744,802 (Schwabel); U.S.Pat. No. 4,770,671 (Monroe et al.) and U.S. Pat. No. 4,881,951 (Wood etal.), the disclosures of which are incorporated herein by reference. Inthe context of the present disclosure, the term “abrasive particles”does not include agglomerated abrasive particles that contain anagglomerate binding material.

Abrasive particles may be coated with materials to provide the particleswith desired characteristics. Abrasive particles may further comprisesurface modification additives including wetting agents (also sometimesreferred to as surfactants) and coupling agents. A coupling agent canprovide an association bridge between the cured particulate binder andthe abrasive particles. Additionally, the coupling agent can provide anassociation bridge between the cured particulate binder and fillerparticles. Examples of coupling agents include but are not limited tosilanes, titanates, and zircoaluminates.

Alternatively, surface coatings can alter and improve the cuttingcharacteristics of the resulting abrasive particle. Such surfacecoatings are described, for example, in U.S. Pat. No. 5,011,508 (Wald etal.); U.S. Pat. No. 3,041,156 (Rowse et al.); U.S. Pat. No. 5,009,675(Kunz et al.); U.S. Pat. No. 4,997,461 (Markhoff-Matheny et al.); U.S.Pat. No. 5,213,591 (Celikkaya et al.); U.S. Pat. No. 5,085,671 (Martinet al.) and U.S. Pat. No. 5,042,991 (Kunz et al.), the disclosures ofwhich are incorporated herein by reference.

The shaped structures of abrasive articles used in accordance withmethods of the present disclosure are typically formed from aroom-temperature solid, sinterable, particulate curable binder in amixture with abrasive particles. The particulate curable bindertypically comprises organic thermosetting and/or thermoplastic material,although this is not a requirement. Suitable particulate curable bindersare typically capable of softening on heating to provide a curableliquid capable of flowing sufficiently so as to be capable of at leastpartially wetting either an abrasive particle surface or the surface ofan adjacent particulate curable binder particle (e.g., sintering).

The particulate curable binder may be any suitable type as long as it iscapable of providing satisfactory abrasive particle bonding and beingactivated or rendered tacky at a temperature which avoids causingsubstantial heat damage or disfiguration to the waterproof backing.Useful particulate curable binders meeting the criteria above includebut are not limited to thermosetting particulate materials,thermoplastic particulate materials, thermosetting/thermoplastic hybridparticulate materials, mixtures of thermosetting particulate materialsand thermoplastic particulate materials, thermoplastic elastomermaterials, and mixtures thereof.

Thermosetting particulate materials involve particles made of atemperature-activated thermosetting resin. Such particles are typicallyused in a solid granular or powder form. The first or short-term effectof a temperature rise sufficiently above the glass transitiontemperature is softening of the material into a flowable fluid-likestate. This change in physical state allows the resin particles tomutually wet or contact the waterproof backing and abrasive particles.In this softened state, the cohesive layer may be modified in shape by,for example, calendering, cutting, or embossing. Prolonged exposure to asufficiently high temperature triggers a chemical reaction, which formsa cross-linked three-dimensional molecular network. The thus solidified(cured) resin particle locally bonds abrasive particles and structuresto the surface of the waterproof backing or the primed waterproofbacking.

Useful thermosetting particulate curable binders include, for example,phenolic resins, epoxy resins, polyester resins, copolyester resins,polyurethane resins, polyamide resins, and mixtures thereof. Usefultemperature-activated thermosetting materials includeformaldehyde-containing resins, such as phenol formaldehyde, novolacphenolics including those with added crosslinking agent (e.g.,hexamethylenetetramine), phenoplasts, and aminoplasts; unsaturatedpolyester resins; vinyl ester resins; alkyd resins, allyl resins; furanresins; epoxies; polyurethanes; cyanate esters; and polyimides. Usefulthermosetting resins include but are not limited to the thermosettingpowders disclosed, for example, in U.S. Pat. No. 5,872,192 (Kaplan, etal.) and U.S. Pat. No. 5,786,430 (Kaplan, et al.), the disclosures ofwhich are incorporated herein by reference.

To prevent heat damage or distortion to the waterproof backing, the curetemperature of the thermosetting particle typically will be below atemperature that will cause damage or deformation of the waterproofbacking constituents.

Useful thermoplastic particulate curable binders may include particulateforms of: polyolefin resins such as polyethylene and polypropylene;polyester and copolyester resins; vinyl resins such as poly(vinylchloride) and vinyl chloride-vinyl acetate copolymers; polyvinylbutyral; cellulose acetate; acrylic resins including polyacrylic andacrylic copolymers such as acrylonitrile-styrene copolymers; andpolyamides (e.g., hexamethylene adipamide, polycaprolactam),co-polyamides; polysulphones; polyethersulphones; aromatic polyethers;polycarbonates; polyarylates; and combinations thereof.

In the case of semi-crystalline thermoplastics (e.g., polyolefins,hexamethylene adipamide, and polycaprolactam, polyethyleneterephthalate), the particulate curable binder may be heated to at leastthe melting point, whereupon they typically become molten to form aflowable fluid.

If non-crystallizing thermoplastics are used (e.g., vinyl resins andacrylic resins), they are typically heated above the glass transitiontemperature and rubbery region until the fluid flow region is reached.

Useful particulate curable binders also include mixtures and blends ofthe foregoing thermosetting and thermoplastic particulate curablebinders.

The size of the particles of particulate curable binder is notparticularly limited. In general, the average particle size is less thanabout 1000 micrometers in diameter, for example, less than about 500micrometers in diameter. Generally, the smaller the size of theparticles of particulate curable binder, the more efficiently they maybe rendered flowable because the surface area of the particles willincrease as the materials are more finely divided.

The amount of particulate curable binder used in the particulate curablebinder-abrasive particle mixture generally will be in the range fromabout 5 weight percent to about 99 weight percent particulate curablebinder, with the remainder about 1 weight percent to about 95 weightpercent comprising abrasive particles and optional fillers. Typically,proportions of the components in the mixture are about 10 to about 90weight percent abrasive particles and about 10 to about 90 weightpercent particulate curable binder, and more typically about 40 to about85 weight percent abrasive particles and about 15 to about 60 weightpercent particulate curable binder, although this is not a requirement.

The particulate curable binder-abrasive particle mixture may include oneor more optional additives, including, for example, additives selectedfrom the group consisting of grinding aids, fillers, wetting agents,chemical blowing agents, surfactants, pigments, coupling agents, dyes,initiators, energy receptors, and mixtures thereof. The optionaladditives may also be selected from the group consisting of potassiumfluoroborate, lithium stearate, glass bubbles, inflatable bubbles, glassbeads, cryolite, polyurethane particles, cork particles, polysiloxanegum, polymeric particles, solid waxes, liquid waxes and mixturesthereof. Optional additives may be included to control a number ofparameters, including particulate curable binder porosity and erosioncharacteristics. The optional additives can be added to the particulatecurable binder, the abrasive particles, or the particulate curablebinder-abrasive particle mixture.

Curing of the particulate curable binder may be accomplished by asuitable method including, for example, by IR heaters, heated rolls,platens, or ovens. Typically the choice of curing conditions are atleast partially dictated by the particular curable binder and waterproofbacking used. The choice of such conditions is well within thecapabilities of one of ordinary skill in the art.

Abrasive articles used in accordance with methods of the presentdisclosure comprise shaped abrasive structures. The abrasive article maycontain a plurality of such shaped abrasive structures in apredetermined array (ordered pattern) on a waterproof backing.Alternatively, the shaped abrasive structures may be in a randomplacement (random pattern) or an irregular placement on the waterproofbacking. Typically, the shaped structures are closely packed in atessellated arrangement across the surface of the waterproof backing,although this is not a requirement. The permanent shaped structures mayinclude voids, which range from about 5 to about 60 percent by volume.

The form of the shaped structures (e.g., curable shaped structures andshaped abrasive structures) may be any of a variety of geometricconfigurations. For example, cross-sections of shaped structures takenparallel to the waterproof backing can be square, circular, rectangular,hexagonal, triangular, or a combination thereof. In some embodiments,shaped structures may have a shape selected from the group consisting ofcones, truncated cones, three-sided pyramids, hexagon-based pyramids,truncated three-sided pyramids, four-sided pyramids, truncatedfour-sided pyramids, rectangular blocks, cubes, erect ribs, erect ribswith rounded distal ends, polyhedrons, and mixtures thereof. Thecross-sectional shape of shaped structures at the base may differ fromthe cross-sectional shape at the distal end. For example, the sidesforming shaped structures may be perpendicular relative to thewaterproof backing, tilted relative to the waterproof backing or taperedwith diminishing width toward the distal end. The transition betweenthese shapes may be smooth and continuous or may occur in discretesteps. A shaped structure with a cross section that is larger at thedistal end than at the attachment end may also be used, althoughfabrication may be more difficult. Shaped structures may also have amixture of different shapes.

The height of each shaped structure is typically substantially the same,but it is possible to have shaped structures of varying heights in asingle abrasive article. The height of the shaped structures generallymay be less than about 10 mm, for example, in a range of from about 0.1to 10 mm, or about 0.5 to about 5 mm, and even more typically about 0.7to about 2 mm. The width of the shaped structure generally ranges fromabout 0.25 to 25 mm or more, for example, between about 1 to 5 mm,although other widths may also be used.

The base of the shaped structures may abut one another or,alternatively, the bases of adjacent shaped abrasive structures may beseparated from one another by some predetermined, typically small,distance.

The areal density of the shaped abrasive structures is typically in arange of from 1,000 to 1,000,000 shaped structures/meter², for example,25,000 to 500,000 shaped structures/meter², or 50,000 to 125,000 shapedstructures/meter², although densities outside of these ranges may beused. The linear spacing may be varied such that the concentration ofstructures is greater in one location than in another. The linearspacing of structures typically ranges from about 0.3 to 10 structuresper linear cm, for example, between 0.5 to about 8 structures per linearcm, although spacings outside of these ranges may be used.

The percentage bearing area may range from about 5 to about 95 percent,typically from about 10 percent to about 80 percent, for example, fromabout 25 percent to about 75 percent, or even from about 30 percent toabout 70 percent. The percent bearing area is the sum of the areas ofthe distal ends times 100 divided by the total area, including openspace, of the waterproof backing upon which the shaped abrasivestructures are deployed.

The shaped structures may be arranged in rows, spiral, helix, or latticefashion, or may be randomly placed.

The shaped structures can be formed by any method that creates thedesired shaped structures. One method comprises softening a sheet ofparticulate curable binder-abrasive particle mixture, forming atemporary shaped structure by a cutting process and then curing thetemporary shaped structure. Another useful method comprises softening asheet of particulate curable binder-abrasive particle mixture, forming atemporary shaped structure by an embossing or molding process and thencuring the temporary shaped structure. Yet another useful methodcomprises forming a temporary shaped structure by a perforated-sheetpatterning process and then curing the temporary shaped structure.

The curable shaped structures comprise a plurality of abrasive particlesmixed with particulate curable binder, but may include other additivessuch as coupling agents, fillers, expanding agents, fibers, antistaticagents, initiators, suspending agents, photosensitizers, lubricants,wetting agents, surfactants, pigments, dyes, UV stabilizers and powderflow additives. The amounts of these additives are selected to providethe properties desired.

Additional coatings may be applied over at least a portion of the shapedstructures. Such coatings, also known as “size” coatings, may becompositionally the same as or different from that of the structures towhich they are applied. Optional additional coatings may be: particulateor liquid in nature, thermoplastic or thermosetting, inorganic ororganic. Such coatings may be applied from solution, or dispersion, ormay be 100 percent solids coatings. Such coatings may or may not includeadditional abrasive particles, abrasive agglomerates, or abrasivecomposites. Examples of suitable coatings include reinforcing resins,lubricants, grinding aids, colorants, or other materials as such tomodify the performance or appearance of the structures.

Optionally, the cured abrasive may be flexed, for example, to improvethe flexibility of the resulting abrasive article by providingseparation (e.g., cracking) between adjacent shaped abrasive structures.

Abrasive articles for use with methods of the present disclosure may beformed from sheet abrasives using any belt forming techniques known tothose in the art, including, for example, adhering opposite ends of thesheet with a splicing tape and splicing adhesive.

Workpieces to be abraded in accordance with methods of the presentdisclosure are fabricated from zirconium in the form of zirconium-basedalloys. The zirconium-based alloys typically comprise greater than 80%zirconium, or in some embodiments, even greater than 95% zirconium alongwith additives selected from, but not limited to, tin (Sn), iron (Fe),chromium (Cr), nickel (Ni), niobium (Nb) and oxygen (O). Specificziconium-based alloys include those disclosed in U.S. Pat. No. 3,136,051(Quinlan et al) and U.S. Pat. No. 5,383,228 (Armijo et al) and U.S. Pat.Pub. No. 2003/0098105 (Jeong et al), the disclosures of which areincorporated herein by reference. Exemplary zirconium-based alloysinclude a class of alloys referred to as “Zircaloy”, including,“Zircaloy-2” and “Zircaloy-4”.

The abrasive articles of the present disclosure can be used with anysuitable machine. In embodiments where the abrasive article is anabrasive belt, it can be used with machines such as, for example,surface grinding machines fitted for abrasive belts, centerless grindingmachines and fixed center roll grinding machines designed for abrasivebelt use or modified for belt use. The abrasive belt is typically in therange of 5 to 35 cm wide and is typically urged against the rotatingworkpiece in increments suitable for the material being ground. Suitableroll grinding machines can readily be converted to accept abrasive beltsand their concomitant contact wheels. Generally, a roll grinding machinewill secure and rotate a cylindrical workpiece to systematically presentits surface for modification. In operation, the cylindrical workpiece istypically rotated in the range of 15 to 92 meters/minute (50 to 300surface feet per minute (sfpm)), and the abrasive belt is typicallydriven in the range of 762 to 2134 meters/minute (2,500 to 7,000 sfpm).In the case of zirconium and titanium workpieces, the abrasive belt istypically driven in the range of 762 to 1067 meters per minute (2,500 to3,500 sfpm.)

The abrasive article of the present disclosure can also be used withcenterless grinding machines. Suitable centerless grinding machinesinclude, for example, Acme (Auburn Hills, Mich.) machine centerless beltgrinders or Cincinnati Machine (now owned by Landis Grinding Systems,Waynesboro, Pa.), or Landis Grinding Systems (Waynesboro, Pa.) bondedwheel centerless machines that are readily converted to accept abrasivebelts and their concomitant contact wheels. Generally, a centerlessgrinding machine will rotate and feed a cylindrical workpiece across arotating abrasive belt to systematically present its surface formodification. In operation, the cylindrical workpiece is typicallyrotated in the range of 15 to 153 meters/minute (50 to 500 sfpm), andthe abrasive belt is typically driven in the range of 762 to 2134 metersper minute (2,500 to 7,000 sfpm.) In the case of zirconium and titaniumworkpieces, the abrasive belt is typically driven in the range of 762 to1067 meters per minute (2,500 to 3,500 sfpm.)

During the abrading operation of the present disclosure, a liquidcoolant can assist in removing heat generated at the abrading interface.The liquid coolant can also aid in swarf or debris removal andlubrication. Examples of liquid coolants useful in the abradingoperation of the present disclosure include water, aqueous mixtures,synthetic, semi-synthetic, and natural oils, water with a soluble oil,and the like, including “CT2552” commercially available from ChemtoolIncorporate, Crystal Lake, Ill., with particular selection of the liquidcoolant being within the level of one of skill in the art. Variousadditives can also be added such as lubricants, surfactants, grindingaids, dispersants, and the like. Selection and application rates ofappropriate liquid coolants is typically dependent upon the selection ofabrasive article, the particular metal being abraded, desired finishingresults, and process limitations.

Using methods of the present disclosure, at least 0.3 (in someembodiments, at least 0.4 or even at least 0.5) grams of material can beremoved from a workpiece per 25.4 millimeter of belt width per minutewhile obtaining a surface finish no greater than 0.22 (in someembodiments, no greater than 0.20, 0.18, 0.16, or even no greater than0.13) micrometer Ra.

Advantages and other embodiments of the methods of the presentdisclosure are further illustrated by the following examples, but theparticular materials and amounts thereof recited in these examples, aswell as other conditions and details, should not be construed to undulylimit this method. All parts and percentages are by weight unlessotherwise indicated.

EXAMPLES

Materials Identification Description Powder A A thermoset copolyesteradhesive powder, commercially available from EMS-CHEMIE (North America)Inc., Sumter, South Carolina, under the trade designation GRILTEX ™D1644E P1 Powder B A thermoplastic copolyester adhesive powder,commercially available from EMS-CHEMIE (North America) Inc., under thetrade designation GRILTEX ™ D1441E P1 Powder C A thermoset epoxy powder,commercially available from 3M Company, St. Paul, Minnesota under thetrade designation SCOTCHKOTE ™ 6258 Powder D A thermoset epoxy powder,commercially available from 3M Company, St. Paul, Minnesota under thetrade designation SCOTCHKOTE ™ 413 Spray Grade Filler A Treated fumedsilica from Cabot Corporation, Tuscola, Illinois, commercially availableunder the trade designation Cab-O-SIL ® CT-1221 Mineral A Grade JIS 1200Black silicon carbide mineral (UKSIC) commercially available from UKAbrasives Inc., Northbrook, Illinois Backing A A woven, polyesterfabric, available from Milliken and Company, Spartanburg, SCcommercially available under the designation 101 × 43, 1.06 Yd./Lb.(at55% relative humidity), Polyester Sateen, High Tenacity, Dry Heat Set1416 mm (55.755 in) Wide Comparative A 4 inch wide by 54 inch longendless SiC abrasive belt, Example A commercially available from the 3MCompany under the trade designation 3M 464W grade 600 Comparative A 4inch wide by 54 inch long (10.2 cm by 137 cm) endless SiC Example Babrasive belt converted using conventional techniques from a largerendless abrasive belt commercially available from VSM Abrasives Company,O'Fallon, Missouri under the trade designation CK918 grade P800Comparative A 4 inch wide by 54 inch long (10.2 cm by 137 cm) endlessSiC Example C abrasive belt converted using conventional techniques froma larger abrasive belt commercially available from Hermes AbrasivesLtd., Virginia Beach, Virginia under the trade designation RB515Y GradeP1200

Example 1

An abrasive belt was made as follows:

Backing A, 8 inches (20.3 cm) wide, was coated using ordinary means witha calcium carbonate filled phenolic backsize coating which was allowedto dry/cure by conventional means.

A primer mixture was prepared by combining Powder A, Powder B and FillerA in the weight ratio of 59.9:40.0:0.1. The primer mixture wasthoroughly blended with an industrial mixer, a Twin Shell Dry Blenderobtained from Patterson Kelly Co. Inc., East Stroudsburg, Pa., for 12minutes.

The waterproof backing was then threaded through a particulatedispensing apparatus, comprising a reservoir and a knife coater, and aheating apparatus in order to coat and at least partially fuse theprimer mixture to at least one of its major surfaces. The primer mixturewas directed to the reservoir of a volumetric single screw powderfeeder. A portion of the primer mixture from the feeder was depositedinto a trough-like reservoir attached to, and behind, the knife coaterof the particulate dispensing apparatus. The rate at which primermixture was added to the reservoir allowed the formation of a bank ofprimer mixture behind the knife coater. The reservoir consisted of twoteflon side walls that mated against the back of the knife coatercreating a seal between the reservoir and knife coater. The width of thereservoir was narrower than the waterproof backing (about 4.5 inches),enabling the waterproof backing to be run under the reservoir sidewalls.The moving backing formed the bottom of the reservoir and, as primermixture entered the reservoir, it landed on the moving backing, saidmoving backing conveyed the primer mixture to the knife coater. Theknife coating blade was adjusted to a gap of 0.010 inches (0.254 mm)above the coated backing to allow a continuous layer of the primerpowder to be deposited on the surface of the waterproof backing as thewaterproof backing was carried forward at a speed of about 7 ft/min(2.13 meters/min). The heating apparatus comprised a 6 ft (1.83 m) long,5 heat-zone platen which was located after the knife coater such that acontinuous process of dispensing the primer via the dispensingapparatus, metering the primer via the knife coater and at leastpartially fusing the primer mixture via the heating apparatus could bemaintained. A coating of the primer mixture, 3.4 grams per 24 squareinches (0.0220 g/cm²), was deposited on the side of the waterproofbacking opposite the backsize coating and at least partially fused bypassing over the heating platen having all zones set at a temperature of265° F. (128° C.). After leaving the heating platen, the primer coatedbacking comprising the at least partially fused primer was air cooledand subsequently wound into a roll by a winder. During the at leastpartial fusing of the primer mixture, it may be possible for at leastsome curing of the primer mixture to occur.

A particulate curable binder-abrasive particle mixture was formed byplacing Mineral A, Powder C and Filler A in the weight ratio of51.5:48.0:0.5 into a plastic container. The container was sealed andplaced on a paint can shaker, model number 5410-00, commerciallyavailable from the Red Devil Equipment Co., Plymouth, Minn. Theparticulate curable binder-abrasive particle mixture was thoroughlyblended by shaking the container for 5 minutes.

The primer coated backing was then threaded through an apparatusdesigned to produce shaped structures. The apparatus included theparticulate dispensing apparatus, knife coater, and heating apparatusdescribed above, a compacting apparatus and an embossing apparatus,arranged such that they could be employed in a continuous process. Thecompacting apparatus was located above the heating apparatus and allowedto come into contact with the layer of the curable binder-abrasivemixture. The compacting apparatus comprised a 3.88 inch (9.9 cm)diameter silicone rubber covered aluminum roll that could spin freely onits shaft and was supported by pivot arms. The contact point of thecompacting roll with the layer of curable binder-abrasive mixture was32.5 inches (82.6 cm) from the end of the platen nearest the particulatedispensing apparatus. The downward load (i.e., dead weight) of thecompacting roll was 6.5 kg.

The embossing apparatus was adjacent to the end of the heating apparatusfurthest from the particulate dispensing apparatus. The embossingstation was comprised of two synchronized rolls. The upper roll was anickel plated, steel embossing roll that contained the desired embossingpattern for the shaped structures. The embossing pattern of theembossing roll was a series of hexagonal shaped cavities comprising a 5inch (12.7 cm) wide continuous circumferential band in the middle of the11 inch (27.9 cm) wide roll having a diameter of 5 inches (12.7 cm). Thehexagonal cavities were packed in a tessellated hexagonal array. Thetips of the hexagon patterns were tipped 10 degrees from the true axisof the roll, i.e. 10 degrees from the cross roll direction. The sides ofthe individual cavities were about 0.080 inches (0.20 cm) long at theouter extremity and the depth of the cavity was about 0.030 inches(0.076 cm) deep. The sides of the cavity were knife-like and had a 52degree included angle. That is, the side was knife-like at the outsidediameter of the embossing roll and then increased in width to the baseof the cavity to form tapered sides that facilitated easy removal of theembossed feature after cooling. The embossing roll was capable of beingtemperature controlled and was held at a set temperature of 90° F. (32°C.). The shape of the base of the cavity was the shape of the top of theformed shaped structure after embossing. The bottom roll was a 5 inch(12.7 cm) diameter, chrome coated, steel roll of similar length as thatof the embossing roll and was capable of being temperature controlled.The set temperature of the bottom roll was 60° F. (16° C.). The gapbetween the embossing roll and the bottom roll was about 0.015 inches(0.38 mm).

Particulate curable binder-abrasive particle mixture was directed to thereservoir of the dispensing apparatus by hand feeding using a plasticcup. The rate at which particulate curable binder-abrasive particlemixture was added to the reservoir allowed the formation of a bank ofparticulate curable binder-abrasive particle mixture behind the knifecoater. The knife coating blade was adjusted to a gap of 0.055 inches(1.40 mm) above the primed backing to allow a continuous layer of theparticulate curable binder-abrasive particle mixture to be deposited onthe primed surface of the waterproof backing at a target thickness of0.055 inches (1.40 mm) as the waterproof backing was carried forward ata speed of about 6 ft/min (1.83 meters/min). The set temperatures of the5 zones of the heated platen were 300° F. (149° C.), 300° F. (149° C.),275° F. (135° C.), 240° F. (116° C.) and 240° F. (116° C.), with thehighest temperatures being near the knife coating apparatus and thelowest temperatures being near the embossing apparatus. After compactingand departing the heating platen, the layer of at least partially fusedparticulate curable binder-abrasive particle mixture entered theembossing apparatus and was embossed with the previously describedhexagon array pattern. The structures, comprising the at least partiallyfused particulate curable binder-abrasive particle mixture, cooled uponthe embossing roll, such that, they maintained the desired shape afterbeing removed from the embossing roll. During the at least partialfusing of the particulate curable binder-abrasive particle mixture, itmay be possible for at least some curing of the particulate curablebinder to occur. Curing of the at least partially fused particulatecurable binder-abrasive particle structures occurred by twice passingthe waterproof backing containing the structures through a 60 ft (18.3meters) long tunnel oven, having a first heat zone of 20 feet (6.1meters) and a second heat zone of 40 feet (12.2 meters). The first passthrough the oven was conducted at 10 feet per minute (3.05meters/minute) with all zones set at a temperature of 190° F. (88° C.).The second pass was conducted at 6.6 feet per minute (2.0 meters/minute)with the first heat zone set at 330° F. (166° C.) and the second heatzone set at 400° F. (204° C.). After cooling, the abrasive belt wasflexed using a 1 inch (2.54 cm) diameter bar using conventionaltechniques. After flexing, 4 inch (10.2 cm) wide by 54 inch (137 cm)endless belts were fabricated from the abrasive belt using conventionaltechniques.

Example 2

Example 1 was repeated with the following changes: The particulatecurable binder-abrasive particle mixture was formed by using Mineral A,Powder A and Filler A in the weight ratio of 48.5:51.0:0.5. The knifecoater blade was adjusted to a gap of 0.053 inches (1.35 mm) above theprimed backing for a target coating thickness of particulate curablebinder-abrasive particle mixture of 0.053 inches (1.35 mm). Thecompacting apparatus was not used. The process speed through the shapedstructure forming apparatus was 3 feet per minute (0.91 meters/minute).The set temperatures of the 5 zones of the heated platen were 325° F.(163° C.), 325° F. (163° C.), 300° F. (149° C.), 300° F. (149° C.) and300° F. (149° C.), with the highest temperatures being near the knifecoating apparatus and the lowest temperatures being near the embossingapparatus. The second pass through the tunnel oven was conducted withthe first heat zone set at 280° F. (138° C.) and the second heat zoneset at 330° F. (166° C.).

Example 3

Example 1 was repeated with the following changes: The particulatecurable binder-abrasive particle mixture was formed by placing MineralA, Powder D and Filler A in the weight ratio of 58.5:41.0:0.5 into a 64oz. plastic container along with 3 1″ rubber balls. The mixture wasthoroughly blended by shaking the container for 10 minutes using thepaint can shaker. The contact point of the compacting roll with thelayer of curable binder-abrasive mixture was 20 inches (50.8 cm) fromthe end of the platen nearest the particulate dispensing apparatus. Theprocess speed through the shaped structure forming apparatus was 3 feetper minute (0.91 meters/minute). The set temperatures of the 5 zones ofthe heated platen were 325° F. (163° C.), 325° F. (163° C.), 325° F.(163° C.), 300° F. (149° C.) and 300° F. (149° C.), with the highesttemperatures being near the knife coating apparatus and the lowesttemperatures being near the embossing apparatus. Curing of the at leastpartially fused particulate curable binder-abrasive particle structuresoccurred by twice passing the waterproof backing containing thestructures through a 30 ft (9.1 meters) long tunnel oven. The first passthrough the oven was conducted at 5 feet per minute (1.52 meters/minute)with all zones set at a temperature of 190° F. (88° C.). The second passwas conducted at 3 feet per minute (0.91 meters/minute) with the ovenset at 390° F. (198° C.).

Example 4

Example 4 was prepared as Example 3 with the exception that thecomposition was Mineral A, Powder D, Powder B, and Filler A in theweight ratio of 60.5:27.3:11.7:0.33. The knife coater blade was adjustedto a gap of 0.052 inches (1.32 mm) above the primed backing for a targetcoating thickness of particulate curable binder-abrasive particlemixture of 0.052 inches (1.32 mm). The contact point of the compactingroll with the layer of curable binder-abrasive mixture was 25 inches(63.5 cm) from the end of the platen nearest the particulate dispensingapparatus.

Example 5

Example 5 was prepared as Example 3 with the exception that thecomposition was Mineral A, Powder D, Powder B, and Filler A in a weightratio of 60.5:15.6:23.4:0.33. The contact point of the compacting rollwith the layer of curable binder-abrasive mixture was 27 inches (68.6cm) from the end of the platen nearest the particulate dispensingapparatus. The knife coater blade was adjusted to a gap of 0.052 inches(1.32 mm) above the primed backing for a target coating thickness ofparticulate curable binder-abrasive particle mixture of 0.052 inches(1.32 mm). The set temperatures of the 5 zones of the heated platen were325° F. (163° C.), 325° F. (163° C.), 325° F. (163° C.), 300° F. (149°C.) and 270° F. (132° C.), with the highest temperatures being near theknife coating apparatus and the lowest temperatures being near theembossing apparatus.

Abrasive Belt Test Procedure 1

The workpieces being abraded by the abrasive belts were about ⅜ inch(9.5 mm) by 30 inch (76 cm) long zirconium alloy tubes comprisingZircaloy. All tube preconditioning and testing was conducted on a ModelM47 Centerless Grinding Machine available from Acme Manufacturing,Auburn Hills, Mich., run at the following conditions. The centerlessgrinding machine was run at a belt speed of 3155 surface feet per minute(962 surface meters per minute), a regulating wheel speed of 82 surfacefeet per minute (25 surface meters per minute), a tube thru feed speedof 4.8 feet/minute (1.5 meters/minute) with a 70 shore A smooth rubbercontact wheel and an amp load over idle of 0.5 to 1.0 amps. A coolant,CT2552 commercially available from Chemtool Incorporate, Crystal Lake,Ill., diluted to 5% by weight in water was used at a flow rate of about0.625 gallons per minute.

A test cycle consisted of the following:

First a 3M 464W grade 320, 4 inch (10.2 cm) wide by 54 inch (137 cm)endless belt, commercially available from the 3M Company, St. Paul,Minn., was mounted on the centerless grinding machine. A set of sixzirconium alloy tubes were preconditioned by running each tubeindividually through the centerless grinding machine for a single pass,i.e., one time through the grinding machine, to generate an approximate20-25 micro-inch Ra surface finish. After the preconditioning, all ofthe tubes were individually weighed and the surface finish was measured.

The 3M 464W grade 320 preconditioning belt was removed from the grindingmachine and the specific belt to be tested was mounted. Tube 1 was runthrough the grinding machine. The surface finish was subsequentlymeasured. Tube 1 was then run through the grinding machine an additional4 passes. After the fifth pass, the tube was reweighed. The amount ofzirconium alloy removed from the tube per pass, i.e., the average cutper pass, was calculated by taking the difference between the pre weightmeasurement (tube weight prior to running through the grinding machine)and post weight measurement (tube weight after 5 passes through thegrinding machine) and dividing the value by 5.

Tube 2 was subsequently run five passes through the grinding machine.The tube was weighed after its fifth pass through the machine and theaverage cut per pass was again calculated. No surface roughnessmeasurement was made on this tube. The belt now had achieved a total often tube passes.

Tubes 3 and 4 were then run through the centerless grinding machine inanalogous fashion to tubes 1 and 2, respectively, including analogousmeasurements for surface finish and cut per pass.

Tubes 5 and 6 were then run through the centerless grinding machine inanalogous fashion to tubes 1 and 2, respectively, including analogousmeasurements for surface finish and cut per pass.

The belt had now achieved a total of 30 tube passes which completed thetest cycle. The test cycle was repeated an additional two times. At theend of the three test cycles, the belt had achieved a total of 90 tubepasses.

Surface Finish Measurement Test Procedure

The resulting surface roughness of the workpiece was determined by usinga surface finish testing device available under the trade designationMAHR® M4PI PERTHOMETER from Feinpruef Corp., Charlotte, N.C.Measurements were made transverse to the scratch patterns with thecut-off length set at 0.03 inches (0.76 mm). The finish indices of Ra,the arithmetic mean of the departures of the profile from the meanlineand Rz (also known as Rtm), which is the mean of the maximumpeak-to-valley values, were recorded for each test.

The abrasive belts of Examples 1 through 5 and Comparative Examples A, Band C, were tested according to the procedures outlined in Abrasive BeltTest Procedure 1. The “average cut per pass” was determined as describedin this same test procedure and the “workpiece surface finish” wasmeasured according to the Surface Finish Test Procedure. Results of thistesting, including, the average cut per pass and workpiece surfacefinish are shown in Tables 1 and 2, respectively.

TABLE 1 Average Cut per Pass (grams) Comparative Comparative ComparativePass Tube Example 1 Example 2 Example 3 Example 4 Example 5 Example AExample B Example C  1-5* 1 1.02 0.67 1.03 1.12 0.67 0.52 0.51 0.57 6-10 2 0.82 0.75 1.10 0.96 0.71 0.59 0.53 0.64 11-15 3 0.81 0.78 0.960.92 0.59 0.48 0.58 0.64 16-20 4 0.81 0.58 0.84 0.89 0.68 0.47 0.48 0.6721-25 5 0.90 0.74 0.91 0.92 0.69 0.34 0.51 0.61 26-30 6 0.85 0.74 0.800.90 0.61 0.39 0.48 0.62 31-35 1 0.81 0.60 0.79 0.97 0.64 0.49 0.42 0.5436-40 2 0.91 0.62 0.98 0.93 0.63 0.50 0.38 0.55 41-45 3 1.12 0.70 0.960.85 0.62 0.50 0.46 0.66 46-50 4 0.91 0.70 0.95 0.86 0.56 0.45 0.45 0.6251-55 5 0.85 0.66 0.86 0.89 0.63 0.39 0.39 0.68 56-60 6 0.85 0.58 0.820.83 0.63 0.39 0.46 0.64 60-65 1 0.70 0.59  n.d¹ n.d. n.d. 0.34 0.450.69 66-70 2 0.68 0.68 n.d n.d n.d 0.33 0.36 0.73 71-75 3 0.69 0.67 n.dn.d n.d 0.34 0.41 0.59 76-80 4 0.74 0.65 n.d n.d n.d 0.34 0.32 0.7481-85 5 0.74 0.63 n.d n.d n.d 0.30 0.32 0.61 86-90 6 0.73 0.73 n.d n.dn.d 0.34 0.42 0.77 Average 0.82 0.67 0.91 0.90 0.64 0.41 0.44 0.65 Std.Dev. 0.11 0.06 0.09 0.04 0.04 0.08 0.07 0.06 n 17 17 11 11 11 17 17 17¹Not determined *Data from passes 1-5 were not included in thecalculation of the average cut and standard deviation, as this isconsidered to be part of the belt break-in period.

TABLE 2 Workpiece Surface Finish: Ra [Rz] (all values in micrometers)Comparative Comparative Comparative Pass Tube Example 1 Example 2Example 3 Example 4 Example 5 Example A Example B Example C  1* 1 0.34[3.12] 0.21 [2.35] 0.38 [3.24] 0.19 [1.90] 0.21 [2.22] 0.33 [3.31] 0.57[4.51] 0.42 [3.67] 11 3 0.23 [2.35] 0.19 [1.85] 0.23 [1.86] 0.19 [1.77]0.14 [1.55] 0.27 [2.65] 0.29 [2.95] 0.21 [2.31] 21 5 0.25 [2.62] 0.17[1.63] 0.24 [1.93] 0.17 [1.63] 0.13 [1.21] 0.23 [2.36] 0.26 [3.28] 0.25[2.69] 31 1 0.17 [1.54] 0.14 [1.75] 0.23 [2.10] 0.17 [1.89] 0.17 [2.09]0.19 [2.24] 0.25 [2.49] 0.28 [2.81] 41 3 0.19 [1.98] 0.13 [1.23] 0.22[1.85] 0.17 [1.69] 0.15 [1.91] 0.24 [2.79] 0.24 [2.82] 0.21 [1.95] 51 50.21 [2.12] 0.14 [1.69] 0.16 [1.44] 0.17 [1.76] 0.12 [1.19] 0.21 [2.73]0.24 [2.70] 0.24 [2.34] 61 1 0.18 [1.80] 0.13 [1.44]  n.d² n.d n.d 0.22[2.84] 0.21 [2.02] 0.25 [2.29] 71 3 0.20 [1.99] 0.13 [1.48] n.d n.d n.d0.24 [3.15] 0.23 [2.60] 0.19 [1.85] 81 5 0.23 [2.06] 0.14 [1.66] n.d n.dn.d 0.27 [3.20] 0.20 [2.40] 0.22 [2.20] Average 0.21 [2.06] 0.14 [1.59]0.22 [2.06] 0.17 [1.59] 0.14 [2.74] 0.23 [2.74] 0.24 [2.66] 0.23 [2.30]Std. Dev. 0.03 [0.33] 0.02 [0.20] 0.03 [0.24] 0.01 [0.10] 0.02 [0.40]0.03 [0.34] 0.03 [0.38] 0.03 [0.33] n 8 [8] 8 [8] 5 [5] 5 [5] 5 [5] 8[8] 8 [8] 8 [8] *Data from pass 1 was not included in the calculation ofthe average Ra and Rz, as well as their standard deviations, as this isconsidered to be part of the belt break-in period. ²Not determined

Surprisingly, Examples 1-3 show a significant improvement in the averagecut per pass, i.e., an increase in the average cut per pass, whileproviding improvement in the workpiece surface finish, i.e., a decreasein the workpiece surface finish, compared to conventional coatedabrasive products. This improvement in average cut per pass isunexpectedly obtained with a finer abrasive grade than ComparativeExamples A and B and a similar abrasive grade to Comparative Example C.Similarly surprising, Example 2 shows improvement in the average cut perpass while providing significant improvement in the workpiece surfacefinish compared to conventional coated abrasive products. Incorporationof a thermoplastic resin shown in Examples 4 and 5 demonstrates theability to maintain the abrasive average cut performance above theComparative Examples while providing substantial improvements in theworkpiece surface finish.

It is to be understood that even in the numerous characteristics andadvantages of the abrasive article of the present disclosure set forthin above description and examples, together with details of thestructure and function of the invention, the disclosure is illustrativeonly. Changes can be made to detail, especially in matters of shape,size and arrangement of the shaped structures and methods of making andusing within the principles of the invention to the full extentindicated by the meaning of the terms in which the appended claims areexpressed and the equivalents of those structures and methods.

1. A method of abrading a zirconium-based alloy workpiece comprising:contacting a zirconium-based alloy workpiece with an abrasive article,wherein the abrasive article comprises: a flexible waterproof backinghaving a first surface bearing a cured primer coating; and a pluralityof shaped structures, each structure having a distal end spaced fromsaid backing and an attachment end attached to the primer coating on thebacking, said shaped structures comprising a mixture of abrasiveparticles having a Knoop hardness greater than 2,200 kg/mm² and curedparticulate binder, wherein the metal workpiece is contacted with thedistal ends of the shaped structures to form an abrading interface;moving the abrasive article relative to the metal workpiece whileproviding sufficient force between the metal workpiece and the distalends of the shaped structures of the abrasive article to abrade themetal workpiece; and applying liquid coolant proximate the abradinginterface.
 2. The method of claim 1 wherein the abrasive particlescomprise silicon carbide.
 3. The method of claim 1 wherein the flexiblewaterproof backing comprises treated woven polyester fabric.
 4. Themethod of claim 1 wherein the liquid coolant comprises water and oil. 5.The method of claim 1 further comprising rotating the workpiece is beingabraded.
 6. The method of claim 1, wherein the abrasive article is anabrasive belt.
 7. The method of claim 6 wherein the abrasive belt ismounted on a centerless grinding machine.
 8. The method of claim 6wherein the abrasive belt is mounted on a fixed center roll grindingmachine.
 9. The method of claim 1 wherein at least a portion of theshaped structures of the abrasive article comprise a cross-sectionselected from the group consisting of square, circular, rectangular,hexagonal, and triangular.
 10. The method of claim 9 wherein the shapedstructures are arranged in a tessellated pattern.
 11. The method ofclaim 9 wherein the shaped structured are formed by an embossingprocess.
 12. The method of claim 9, wherein the zirconium-based alloyworkpiece is cylindrical.
 13. A method of abrading a cylindricalzirconium-based alloy workpiece comprising: contacting a cylindricalzirconium-based alloy workpiece with an abrasive article, wherein theabrasive article comprises: a flexible waterproof backing having a firstsurface bearing a cured primer coating; and a plurality of shapedstructures, each structure having a distal end spaced from said backingand an attachment end attached to the primer coating on the backing,said shaped structures comprising a mixture of silicon carbide abrasiveparticles and a cured thermoset particulate binder, wherein the metalworkpiece is contacted with the distal ends of the shaped structures toform an abrading interface; moving the abrasive article relative to themetal workpiece while providing sufficient force between the metalworkpiece and the distal ends of the shaped structures of the abrasivearticle to abrade the metal workpiece; and applying liquid coolantproximate the abrading interface.
 14. The method of claim 13 wherein thesilicon carbide abrasive particles have an average particle size in therange of 4 to 40 micrometers.
 15. The method of claim 13 wherein theflexible waterproof backing comprises treated woven polyester fabric.16. The method of claim 13 wherein the liquid coolant comprises waterand oil.
 17. The method of claim 13 further comprising rotating theworkpiece is being abraded.
 18. The method of claim 13, wherein theabrasive article is an abrasive belt.
 19. The method of claim 18 whereinthe abrasive belt is mounted on a centerless grinding machine.
 20. Themethod of claim 18 wherein the abrasive belt is mounted on a fixedcenter roll grinding machine.
 21. The method of claim 13 wherein atleast a portion of the shaped structures of the abrasive articlecomprise a cross-section selected from the group consisting of square,circular, rectangular, hexagonal, and triangular.
 22. The method ofclaim 21 wherein the shaped structured are formed by an embossingprocess.
 23. The method of claim 18 wherein at least 0.3 grams ofmaterial is removed from the workpiece per 25.4 millimeter of belt widthper minute, and a surface finish no greater than 0.22 micrometers Ra isobtained.
 24. A method of abrading a zirconium-based alloy cylindricalworkpiece comprising: contacting a cylindrical zirconium-based alloyworkpiece with an abrasive article, wherein the abrasive articlecomprises: a flexible waterproof backing having a first surface bearinga cured primer coating; and a plurality of shaped structures, eachstructure having a distal end spaced from said backing and an attachmentend attached to the primer coating on the backing, said shapedstructures comprising a mixture of abrasive particles having a Knoophardness greater than 2,200 kg/mm² and a mixture of cured thermoplasticand thermoset particulate binder, wherein the metal workpiece iscontacted with the distal ends of the shaped structures to form anabrading interface; moving the abrasive article relative to the metalworkpiece while providing sufficient force between the metal workpieceand the distal ends of the shaped structures of the abrasive article toabrade the metal workpiece; and applying liquid coolant proximate theabrading interface.
 25. The method of claim 24 wherein the abrasivearticle is an abrasive belt.
 26. The method of claim 25 wherein at least0.3 grams of material is removed from the workpiece per 25.4 millimeterof belt width per minute, and a surface finish no greater than 0.22micrometers Ra is obtained.
 27. The method of claim 25 wherein at least0.3 grams of material is removed from the workpiece per 25.4 millimeterof belt width per minute, and a surface finish no greater than 0.20micrometers Ra is obtained.
 28. The method of claim 25 wherein at least0.3 grams of material is removed from the workpiece per 25.4 millimeterof belt width per minute, and a surface finish no greater than 0.13micrometers Ra is obtained.